Bacterial conjugation in Escherichia coli K-12 requires recipient cell functions to achieve gene transmission by cell-to-cell pairing. The concept that membranes contain structural, organizational, or catalytic proteins and other macromolecules with functional roles in conjugation can be resolved in a rigorous fashion using conjugation-deficient (Con-) mutants. A collection of Con- mutants has been isolated by a variety of indirect selective techniques, all of which involve recovery of mutants with defects in functions thought to be involved with membranes (Falkinham and Curtiss, 1976). Because of the development of techniques to influence and measure the conformational changes and to identify the protein and lipopolysaccharide (LPS) composition of bacterial membranes it is possible to describe membrane-associated events and functional macromolecules involved in conjugation. The specific objectives of the proposed research include: (1) mapping mutations which result in a Con- phenotype, (2) description of the conformational changes of membranes during conjugation using fluorescent membrane probes, (3) identification of the proteins with functional roles in conjugation by associating changes in inner and outer membrane proteins with mutations resulting in a Con- phenotype using the techniques of selective detergent solubilization and acrylamide gel electrophoresis, (4) identification of the chemical nature of the donor pilus receptor, using phage and lectin adsorption and chemical techniques to describe LPS composition in Con plus and Con minus strains, and (5) determination of the role of membrane subunit mobility during conjugation by manipulating the unsaturated fatty acid composition of membranes of a recipient strain of E. coli K-12.